As a structure for installing a child seat to a vehicle seat, it is well known to place a child seat on a vehicle seat and to fix the child seat to the vehicle seat by routing a seat belt of the vehicle seat over the child seat (for example, Japanese Unexamined Patent Application Publication No. 2001-347860).
Also, as a seat belt, an airbelt having an expandable portion, which expands by bringing in a gas from an inflator, is known (for example, Japanese Unexamined Patent Application Publication No. 2005-239055). An airbelt of the above publication includes a normal belt portion (called webbing in the publication), which is fabricated of a non-expandable belt material as with a normal seat belt, and a lap bag that is an expandable portion disposed along the normal belt portion.
One end of the normal belt portion is connected to one of side frames of a vehicle seat using a lap anchor, and the other end side is connected to a seat belt retractor so as to be retractable. A middle portion of the normal belt portion is threaded through a tang, and moreover, the seat belt retractor side with respect to the tang is threaded through a shoulder anchor. This normal belt portion is routed to the front side of the vehicle seat as with a normal seat belt and its tang is connected to a buckle device.
A part of the normal belt portion between the tang and the shoulder anchor constitutes a shoulder portion and a part between the tang and the lap anchor constitutes a lap portion. This lap portion is provided with the above lap bag.
In an emergency case such as a vehicle collision or the like, an inflator is activated to blow a gas, which flows from the inflator into the lap bag and allows the lap bag to expand.
In a vehicle seat that is provided with an airbelt, there is a case that a child seat is fixed to the vehicle seat by routing the airbelt over the child seat as a seat belt. In this case, when an expandable portion of the airbelt expands, there is a fear that the expanded expandable portion interferes with the child seat, which may adversely affect each other.